Openbravo ERP supports PostgreSQL as its database engine.
For the specific versions supported and the currently recommended version check the System Requirements.
In general you should never pick a version lower then the recommended ones, but are free to pick higher version if they are supported.
In additions to the PostgreSQL server the the UUID contrib package is required.
PostgreSQL documentation and tutorials are available at:
Setting up the numeric locale
Since PostgreSQL 9.3 a behavior change has been introduced in the to_number() database procedure .
Previously, a period was considered to be a decimal point even when the locale says it isn't. Since PostgreSQL 9.3, the lc_numeric setting is considered to the set decimal format.
This new behavior can impact when retrieving decimal numbers in the database. In order to avoid this problem and continue considering the period as the database decimal separator, the lc_numeric setting should be configured as follows, in postgresql.conf file:
lc_numeric = 'en_US.UTF-8'
When running PostgreSQL on windows the equivalent setting is slightly different
lc_numeric = 'English_United States.1252'
Once done, remember to reload the database server:
Installing PostgreSQL on Microsoft Windows
Follow the instructions on the PostgreSQL wiki.
On the PostgreSQL download page there is an installer available which also directly includes the UUID extension mentioned as required above.
At the end of using this installer it will ask to optionally launch a 'StackBuilder' program to install more Addon software. None of this its required for Openbravo so that step can be safely skipped.
Installing PostgreSQL on RedHat
yum install postgresql postgresql-contrib